This application corresponds to German Application No. 101 45 990.4 filed Sep. 18, 2001, which is herein incorporated by reference in its entirety.
1. Field of the Invention
This invention relates generally to a hydrostatic transmission with a pump and a motor, each of which is designed as an axial piston engine utilizing a swashplate design, wherein the pump and the motor are arranged coaxially one behind the other and are connected to each other.
2. Technical Considerations
A known hydrostatic transmission is described in DE-OS 19 45 440.
An object of this invention is to provide a hydrostatic transmission of the general type described above but which is compact and can be used in an expanded range of potential applications.
The invention provides a hydrostatic transmission in which the motor has a hollow output shaft through which is routed a power take-off shaft driven by a drive shaft of the pump. It is, therefore, possible to use the driving motor, which is coupled with the drive shaft of the pump, to drive an additional unit, for example an auxiliary pump, whereby this is done centrally through the hydrostatic transmission comprising the pump and the motor. The hydrostatic transmission of the invention thereby has compact dimensions.
In one configuration of the invention that is advantageous in terms of its compact construction, the swashplate of the pump and the swashplate of the motor can be located on opposite ends of the hydrostatic transmission. A common control base mount can be located axially between the cylinder drum of the pump and the cylinder drum of the motor and can be provided with supply channels.
The power take-off shaft can be mounted inside the output shaft of the motor. In a particular embodiment of the invention, however, it is also possible to configure the power take-off shaft in the form of a torque rod that is free of radial stress.
In one advantageous configuration of the invention, the motor can be a variable displacement motor. A fixed displacement motor can also be used in the hydrostatic transmission taught by the invention.
As a result of the realization of the output shaft of the motor in the form of a hollow shaft, the torque that can be transmitted is lower than if the shaft were in the form of a solid shaft. It has been found to be advantageous if the motor is sized larger than is necessary for the torque that can be taken off the hydrostatic transmission, whereby the torque can be adjusted by reducing the pivoting angle of the swashplate. The full torque that the motor can generate on the basis of its size is thereby not exerted on the output shaft of the motor. This measure makes it possible to realize the output shaft in the form of a hollow shaft, which naturally can transmit only a lower torque than the torque that could be transmitted by a solid shaft of the same diameter.